Gate Driver on Array, GOA technology can help to fabricate narrow border or borderless display products, and it can reduce the binding process for the external integrated circuit, IC in addition it is conducive to enhance productivity and reduce product costs, and has been widely used and research. Currently, Indium Gallium Zinc Oxide, IGZO is used to make a GOA circuit because of its high mobility and good device stability which reduces the complexity of a GOA circuit. In particular, because of its high mobility, when used in the fabrication of thin film transistors in GOA circuits, the size of the thin film transistor is lower relative to the thin film transistor fabricated using amorphous silicon, a-Si, which is conducive to the production of a narrow-border display; at the same time, due to the good device stability, it is possible to reduce the number of power supplies and thin film transistors for stabilizing the performance of the thin film transistor, and then to create a relatively simple GOA circuit, and reduce power consumption.
Referring to FIG. 1, FIG. 1 is a partial circuit diagram of a GOA circuit in the conventional technology, wherein the GOA circuit is formed by IGZO. Since the initial electrical characteristics of the IGZO are easily formed as a depletion-mode semiconductor thin film transistor, such a transistor has a negative value turn on voltage Vth, and in the GOA circuit, the transistor T32 and T42 in the pull down maintaining unit (shown in the dashed box in FIG. 1) is affected by the material, the turn on voltage Vth being positively shifted it can be seen that when the thin film transistor fabricated by IGZO is used in the pull down maintaining unit, a turn on voltage Vth in negative value is likely to occur, resulting in a forward voltage shift.